As an electrically rewritable (A word of rewritable means that it is programmable) non-volatile memory, there has been proposed a so-called flash memory capable of carrying out a write processing and an erase processing on a comparatively large unit such as a batch erase processing on a memory block unit and a page write processing on a word line unit or an EEPROM (Electrically Erasable and Programmable Read Only Memory) capable of carrying out a write processing and an erase processing on a unit of a byte or word to be a calculation processing unit by a CPU. A microcomputer for carrying out on-chip over the EEPROM and a microcomputer for carrying out the on-chip over the flash memory have been proposed, respectively. An example of the document describing the former microcomputer includes JP-A-63-266698. An example of the document describing the latter microcomputer includes JP-A-05-266219.